Set up a render farm with multiple OS and spec
You could install BURP on one or more machines, and the BOINC client on the rest. That way you don't have to worry too much about the composition of your farm. This is what we also use on Renderfarm.fi as our backend.

BURP: http://development.burp.renderfarming.net/projects/burp/wiki/How_to_download_the_code